mavlink: add class for command retransmission

This adds a class to allow for retransmission of outgoing commands.
The sent commands are kept in a timestamped list to check if they are
acked as required by the mavlink protocol.
If they are not acked within a timeout, they can be retransmitted.

src/modules/mavlink/CMakeLists.txt

@@ -1,6 +1,6 @@
 ############################################################################
 #
-#   Copyright (c) 2015 PX4 Development Team. All rights reserved.
+#   Copyright (c) 2015-2017 PX4 Development Team. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
@@ -53,6 +53,7 @@ px4_add_module(
 		mavlink_log_handler.cpp
 		mavlink_shell.cpp
 		mavlink_ulog.cpp
+		mavlink_command_sender.cpp
 	DEPENDS
 		platforms__common
 	)

src/modules/mavlink/mavlink_command_sender.cpp

@@ -0,0 +1,230 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file mavlink_command_sender.cpp
+ * Mavlink commands sender with support for retransmission.
+ *
+ * @author Julian Oes <julian@oes.ch>
+ */
+
+#include "mavlink_command_sender.h"
+#include <px4_log.h>
+#include <cassert>
+
+bool MavlinkCommandSender::_init = false;
+MavlinkCommandSender *MavlinkCommandSender::_instance = nullptr;
+px4_sem_t MavlinkCommandSender::_lock;
+
+void MavlinkCommandSender::initialize()
+{
+	if (_init) {
+		return;
+	}
+
+	px4_sem_init(&_lock, 1, 1);
+	_init = true;
+}
+
+MavlinkCommandSender &MavlinkCommandSender::instance()
+{
+	if (_instance == nullptr) {
+		_instance = new MavlinkCommandSender();
+	}
+
+	return *_instance;
+}
+
+MavlinkCommandSender::MavlinkCommandSender() :
+	_commands(5)
+{
+}
+
+MavlinkCommandSender::~MavlinkCommandSender()
+{
+	px4_sem_destroy(&_lock);
+}
+
+int MavlinkCommandSender::handle_vehicle_command(struct vehicle_command_s &command, mavlink_channel_t channel)
+{
+	assert(0 <= channel);
+	assert(channel < MAX_MAVLINK_CHANNEL);
+
+	lock();
+	PX4_INFO("getting vehicle command with timestamp %" PRIu64 ", channel: %d", command.timestamp, channel);
+
+	mavlink_command_long_t msg = {};
+	msg.target_system = command.target_system;
+	msg.target_component = command.target_component;
+	msg.command = command.command;
+	msg.confirmation = command.confirmation;
+	msg.param1 = command.param1;
+	msg.param2 = command.param2;
+	msg.param3 = command.param3;
+	msg.param4 = command.param4;
+	msg.param5 = command.param5;
+	msg.param6 = command.param6;
+	msg.param7 = command.param7;
+	mavlink_msg_command_long_send_struct(channel, &msg);
+
+	bool already_existing = false;
+	_commands.reset_to_start();
+
+	while (command_item_t *item = _commands.get_next()) {
+		if (item->timestamp_us == command.timestamp) {
+
+			// We should activate the channel by setting num_sent_per_channel from -1 to 0.
+			item->num_sent_per_channel[channel] = 0;
+
+			PX4_INFO("already existing");
+			already_existing = true;
+
+			break;
+		}
+	}
+
+	if (!already_existing) {
+
+		command_item_t new_item;
+		new_item.command = msg;
+		new_item.timestamp_us = command.timestamp;
+		new_item.num_sent_per_channel[channel] = 0;
+		new_item.last_time_sent_us = hrt_absolute_time();
+		_commands.put(new_item);
+	}
+
+	unlock();
+	return 0;
+}
+
+void MavlinkCommandSender::handle_mavlink_command_ack(const mavlink_command_ack_t &ack,
+		uint8_t from_sysid, uint8_t from_compid)
+{
+	PX4_INFO("handling result %d for command %d: %d from %d, %d",
+		 ack.result, ack.command, from_sysid, from_compid);
+	lock();
+
+	_commands.reset_to_start();
+
+	while (command_item_t *item = _commands.get_next()) {
+		// Check if the incoming ack matches any of the commands that we have sent.
+		if (item->command.command == ack.command &&
+		    from_sysid == item->command.target_system &&
+		    from_compid == item->command.target_component) {
+			PX4_INFO("handling result %d for command %d: %d", ack.result, ack.command);
+			// Drop it anyway because the command seems to have arrived at the destination, even if we
+			// receive IN_PROGRESS because we trust that it will be handled after that.
+			_commands.drop_current();
+			break;
+		}
+	}
+
+	unlock();
+}
+
+void MavlinkCommandSender::check_timeout(mavlink_channel_t channel)
+{
+	assert(0 <= channel);
+	assert(channel < MAX_MAVLINK_CHANNEL);
+
+	lock();
+
+	_commands.reset_to_start();
+
+	while (command_item_t *item = _commands.get_next()) {
+		if (hrt_elapsed_time(&item->last_time_sent_us) <= TIMEOUT_US) {
+			// We keep waiting for the timeout.
+			continue;
+		}
+
+		// The goal of this is to retry from all channels. Therefore, we keep
+		// track of the retry count for each channel.
+		//
+		// When the first channel does a retry, the timeout is reset.
+		// (e.g. all channel have done 2 retries, then channel 0 is called
+		// and does retry number 3, and also resets the timeout timestamp).
+
+		// First, we need to determine what the current max and min retry level
+		// are because we can only level up, if all have caught up.
+		// If num_sent_per_channel is at -1, the channel is inactive.
+		int8_t max_sent = 0;
+		int8_t min_sent = INT8_MAX;
+
+		for (unsigned i = 0; i < MAX_MAVLINK_CHANNEL; ++i) {
+			if (item->num_sent_per_channel[i] > max_sent) {
+				max_sent = item->num_sent_per_channel[i];
+			}
+
+			if ((item->num_sent_per_channel[i] != -1) &&
+			    (item->num_sent_per_channel[i] < min_sent)) {
+				min_sent = item->num_sent_per_channel[i];
+			}
+		}
+
+		if (item->num_sent_per_channel[channel] < max_sent) {
+			// We are behind and need to do a retransmission.
+			mavlink_msg_command_long_send_struct(channel, &item->command);
+			item->num_sent_per_channel[channel]++;
+
+			PX4_INFO("%x timeout (behind), retries: %d/%d, channel: %d",
+				 item, item->num_sent_per_channel[channel], max_sent, channel);
+
+		} else if (item->num_sent_per_channel[channel] == max_sent &&
+			   min_sent == max_sent) {
+
+			// If the next retry would be above the needed retries anyway, we can
+			// drop the item, and continue with other items.
+			if (item->num_sent_per_channel[channel] + 1 > RETRIES) {
+				_commands.drop_current();
+				PX4_INFO("%x, timeout dropped", item);
+				continue;
+			}
+
+			// We are the first of a new retransmission series.
+			mavlink_msg_command_long_send_struct(channel, &item->command);
+			item->num_sent_per_channel[channel]++;
+			// Therefore, we are the ones setting the timestamp of this retry round.
+			item->last_time_sent_us = hrt_absolute_time();
+
+			PX4_INFO("%x timeout (first), retries: %d/%d, channel: %d",
+				 item, item->num_sent_per_channel[channel], max_sent, channel);
+
+		} else {
+			// We are already ahead, so this should not happen.
+			// If it ever does, just ignore it. It will timeout eventually.
+			continue;
+		}
+	}
+
+	unlock();
+}

src/modules/mavlink/mavlink_command_sender.h

@@ -0,0 +1,125 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file mavlink_command_sender.h
+ * Mavlink commands sender with support for retransmission.
+ *
+ * @author Julian Oes <julian@oes.ch>
+ */
+
+#pragma once
+
+#include <px4_tasks.h>
+#include <px4_sem.h>
+#include <drivers/drv_hrt.h>
+
+#include <uORB/topics/vehicle_command.h>
+#include <uORB/topics/vehicle_command_ack.h>
+
+#include "timestamped_list.h"
+#include "mavlink_bridge_header.h"
+#include <v2.0/mavlink_types.h>
+
+/**
+ * @class MavlinkCommandSender
+ */
+class MavlinkCommandSender
+{
+public:
+	/**
+	 * initialize: call this once on startup (this function is not thread-safe!)
+	 */
+	static void initialize();
+
+	static MavlinkCommandSender &instance();
+
+	/**
+	 * Send a command on a channel and keep it in a queue for retransmission.
+	 * thread-safe
+	 * @return 0 on success, <0 otherwise
+	 */
+	int handle_vehicle_command(struct vehicle_command_s &command, mavlink_channel_t channel);
+
+	/**
+	 * Check timeouts to verify if an commands need retransmission.
+	 * thread-safe
+	 */
+	void check_timeout(mavlink_channel_t channel);
+
+	/**
+	 * Handle mavlink command_ack.
+	 * thread-safe
+	 */
+	void handle_mavlink_command_ack(const mavlink_command_ack_t &ack, uint8_t from_sysid, uint8_t from_compid);
+
+private:
+	MavlinkCommandSender();
+
+	~MavlinkCommandSender();
+
+	static void lock()
+	{
+		do {} while (px4_sem_wait(&_lock) != 0);
+	}
+
+	static void unlock()
+	{
+		px4_sem_post(&_lock);
+	}
+
+
+	static bool _init;
+	static MavlinkCommandSender *_instance;
+
+	static px4_sem_t _lock;
+
+	// There are MAVLINK_COMM_0 to MAVLINK_COMM_3, so it should be 4.
+	static const unsigned MAX_MAVLINK_CHANNEL = 4;
+
+	typedef struct {
+		mavlink_command_long_t command = {};
+		hrt_abstime timestamp_us = 0;
+		hrt_abstime last_time_sent_us = 0;
+		int8_t num_sent_per_channel[MAX_MAVLINK_CHANNEL] = {-1, -1, -1, -1};
+	} command_item_t;
+
+	TimestampedList<command_item_t> _commands;
+
+	static const uint8_t RETRIES = 3;
+	static const uint64_t TIMEOUT_US = 500000;
+
+	/* do not allow copying or assigning this class */
+	MavlinkCommandSender(const MavlinkCommandSender &) = delete;
+	MavlinkCommandSender operator=(const MavlinkCommandSender &) = delete;
+};

src/modules/mavlink/mavlink_main.cpp

@@ -85,6 +85,7 @@
 #include "mavlink_messages.h"
 #include "mavlink_receiver.h"
 #include "mavlink_rate_limiter.h"
+#include "mavlink_command_sender.h"
 
 // Guard against MAVLink misconfiguration
 #ifndef MAVLINK_CRC_EXTRA
@@ -2450,6 +2451,7 @@ int
 Mavlink::start(int argc, char *argv[])
 {
 	MavlinkULog::initialize();
+	MavlinkCommandSender::initialize();
 
 	// Wait for the instance count to go up one
 	// before returning to the shell

src/modules/mavlink/mavlink_messages.cpp

@@ -44,6 +44,7 @@
 
 #include "mavlink_main.h"
 #include "mavlink_messages.h"
+#include "mavlink_command_sender.h"
 
 #include <commander/px4_custom_mode.h>
 #include <drivers/drv_pwm_output.h>
@@ -453,25 +454,14 @@ protected:
 		struct vehicle_command_s cmd;
 
 		if (_cmd_sub->update(&_cmd_time, &cmd)) {
+
 			/* only send commands for other systems/components */
-			if (cmd.target_system != mavlink_system.sysid || cmd.target_component != mavlink_system.compid) {
-				mavlink_command_long_t msg = {};
-
-				msg.target_system = cmd.target_system;
-				msg.target_component = cmd.target_component;
-				msg.command = cmd.command;
-				msg.confirmation = cmd.confirmation;
-				msg.param1 = cmd.param1;
-				msg.param2 = cmd.param2;
-				msg.param3 = cmd.param3;
-				msg.param4 = cmd.param4;
-				msg.param5 = cmd.param5;
-				msg.param6 = cmd.param6;
-				msg.param7 = cmd.param7;
-
-				mavlink_msg_command_long_send_struct(_mavlink->get_channel(), &msg);
-			}
+			//if (cmd.target_system != mavlink_system.sysid || cmd.target_component != mavlink_system.compid) {
+			MavlinkCommandSender::instance().handle_vehicle_command(cmd, _mavlink->get_channel());
+			//}
 		}
+
+		MavlinkCommandSender::instance().check_timeout(_mavlink->get_channel());
 	}
 };
 

src/modules/mavlink/mavlink_receiver.cpp

@@ -88,6 +88,7 @@
 #include "mavlink_bridge_header.h"
 #include "mavlink_receiver.h"
 #include "mavlink_main.h"
+#include "mavlink_command_sender.h"
 
 static const float mg2ms2 = CONSTANTS_ONE_G / 1000.0f;
 
@@ -628,6 +629,8 @@ MavlinkReceiver::handle_message_command_ack(mavlink_message_t *msg)
 	mavlink_msg_command_ack_decode(msg, &ack);
 
 	if (ack.result != MAV_RESULT_ACCEPTED && ack.result != MAV_RESULT_IN_PROGRESS) {
+		MavlinkCommandSender::instance().handle_mavlink_command_ack(ack, msg->sysid, msg->compid);
+
 		if (msg->compid == MAV_COMP_ID_CAMERA) {
 			PX4_WARN("Got unsuccessful result %d from camera", ack.result);
 		}

src/modules/mavlink/timestamped_list.h

@@ -0,0 +1,158 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file timestamped list.h
+ * Fixed size list with timestamps.
+ *
+ * The list has a fixed size that is set at instantiation and is based
+ * on timestamps. If a new value is put into a full list, the oldest value
+ * is overwritten.
+ *
+ * @author Julian Oes <julian@oes.ch>
+ */
+
+#pragma once
+
+#include <drivers/drv_hrt.h>
+
+/**
+ * @class TimestampedList
+ */
+template <class T>
+class TimestampedList
+{
+public:
+	TimestampedList(int num_items)
+	{
+		_list = new item_t[num_items];
+		_list_len = num_items;
+	}
+	~TimestampedList()
+	{
+		delete[] _list;
+	}
+
+	/*
+	 * Insert a value into the list, overwrite the oldest entry if full.
+	 */
+	void put(T new_value)
+	{
+		hrt_abstime now = hrt_absolute_time();
+
+		// Insert it wherever there is a free space.
+		for (int i = 0; i < _list_len; ++i) {
+			if (_list[i].timestamp_us == 0) {
+				_list[i].timestamp_us = now;
+				_list[i].value = new_value;
+				return;
+			}
+		}
+
+		// Find oldest entry.
+		int oldest_i = 0;
+
+		for (int i = 1; i < _list_len; ++i) {
+			if (_list[i].timestamp_us < _list[oldest_i].timestamp_us) {
+				oldest_i = i;
+			}
+		}
+
+		// And overwrite oldest.
+		_list[oldest_i].timestamp_us = now;
+		_list[oldest_i].value = new_value;
+	}
+
+	/*
+	 * Before iterating using get_next(), reset to start.
+	 */
+	void reset_to_start()
+	{
+		_current_i = -1;
+	}
+
+	/*
+	 * Iterate through all active values (not sorted).
+	 * Return nullptr if at end of list.
+	 *
+	 * This is basically a poor man's iterator.
+	 */
+	T *get_next()
+	{
+		// Increment first, then leave it until called again.
+		++_current_i;
+
+		for (int i = _current_i; i < _list_len; ++i) {
+			if (_list[i].timestamp_us != 0) {
+				_current_i = i;
+				return &_list[i].value;
+			}
+		}
+
+		return nullptr;
+	}
+
+	/*
+	 * Disable the last item that we have gotten.
+	 */
+	void drop_current()
+	{
+		if (_current_i < _list_len) {
+			_list[_current_i].timestamp_us = 0;
+		}
+	}
+
+	/*
+	 * Update the timestamp of the item we have gotten.
+	 */
+	void update_current()
+	{
+		if (_current_i < _list_len) {
+			_list[_current_i].timestamp = hrt_absolute_time();
+		}
+	}
+
+	/* do not allow copying or assigning this class */
+	TimestampedList(const TimestampedList &) = delete;
+	TimestampedList operator=(const TimestampedList &) = delete;
+
+private:
+	typedef struct {
+		hrt_abstime timestamp_us = 0; // 0 signals inactive.
+		T value;
+	} item_t;
+
+	item_t *_list = nullptr;
+	int _list_len = 0;
+	int _current_i = -1;
+};